Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pasteur!ucbvax!decwrl!labrea!rutgers!att!alberta!ubc-cs!van-bc!ve7apu!spraggs
From: spraggs@ve7apu.UUCP ( VE7ADE)
Newsgroups: comp.sys.mac
Subject: Re: SIMM pinout
Message-ID: <296@ve7apu.UUCP>
Date: 30 Mar 89 07:29:16 GMT
References: <25017@amdcad.AMD.COM>
Reply-To: spraggs@ve7apu.UUCP (John Spraggs - VE7ADE)
Organization: Doug Lockhart VE7APU Richmond, B.C.
Lines: 26


This is the pinout for a 1 Meg SIMM.  I have shown the assignments for
a 9 bit part for completeness.  The ninth chip is missing on a Mac SIMM
so these (*) are NC as well.

A 256k part is NC on A9.  I expect a 4 Meg part puts A10 on pin 19 and a
16 Meg one has A11 on pin 24.

X        ___
X    Vcc CAS DQ1 A0 A1 DQ2 A2 A3 Vss DQ3 A4 A5 DQ4 A6 A7 .. continued in line
X     1                                               15
X  
X                     _                   ___ ___
X .. DQ5 A8 A9 NC DQ6 W Vss DQ7 NC DQ8 Q9 RAS CAS9 D9 Vcc
X    16                                *       *   *  30

Vcc = +5V    Vss = ground  DQ = Data I/O   A = Address
___                            ___
CAS = Column Address Strobe    RAS = Row Address Strobe

Since the Mac + at least does not pull down D9 or CAS9, by 9 SIMMs 
should not be used since these inputs can float through the mid voltage
region.  When this happens excessive current flows, causing over heating
and possibly enough noise to corrupt data.

John Spraggs